Scraping, i.e. removing sediment or other undesirable material that has become deposited on the bottom of a drain or more generally of a gallery, raises a certain number of problems. The machine of the invention relates more particularly to a system that makes it possible to scrap sewers in a drainage network for conveying waste water or the like. As time progresses, material settles on the bottoms of the galleries constituting such drains. The operator periodically subcontracts the work of scraping said galleries.
At present, such galleries are usually scraped by the following technique:                a dam is set up so as to enable the gallery for scraping to be unwatered; and        scraping is performed by a self-propelled loader, e.g. of the type used in mines, having a bucket fitted with a blade for scraping the bottom of the gallery. Once the bucket is full, the loader needs to perform a go-and-return trip between the scraping front and an access point to the surface where the bucket can be emptied. The bucket of the loader is emptied by filling a skip, that is then raised by means of a crane in order to be taken away. Such a solution is described in French patent No. 2 701 278.        
The main drawback of such a drain scraper machine is that while the scraper vehicle is traveling, scraping is interrupted. It will be understood that as the distance between the scraping front and the point for removing recovered sediment increases, so the productivity of the machine decreases.
In addition, the type of vehicle described in the prior art usually consists in a mechanical digger type machine with conventional crawler tracks and it requires the gallery that is to be treated to be unwatered. It will be understood that the necessity for the machine to perform go-and-return trips between the scraping front and the unloading zone leads to long periods during which the scraping machine is not scraping. This leads to a very significant reduction in the efficiency of the machine.